Here's a quick tip if you have some side loaded apps on windows 8/RT and your developer licence has expired. When this happens the apps have a cross on them and are unable to open taking you to the store.

Problem

Error "Your developer license has expired. To continue to use this app, please renew your license"

Solution

Open PowerShell with admin privileges and execute the following command

Show-WindowsDeveloperLicenseRegistration

This will prompt you through the same dialog as when installing your first side loaded app. A developer Licence expires every month so a quick script to bring up this prompt could be handy.